Reactivity of hybridomas derived from T cells activated in vivo during graft-versus-host disease.

To examine the specificity of T helper cells activated during murine graft-vs-host disease (GVHD), T cell hybridomas from GVHD spleens and livers were generated and analyzed. CTL-depleted C57BL/6 (B6) donor cells were injected into irradiated (B6 x bm12)F1 or (bm1 x bm12)F1 recipient mice. Five or fourteen days later, cells from livers and spleens were fused directly with the TCR-deficient (alpha beta)- BW5147 thymoma line. The in vivo-activated T cells produced hybridomas as efficiently as either T cells activated in a primary mixed lymphocyte reaction or expanded in vitro after isolation from GVHD mice. Overall, 91% (396 of 437) of hybridomas generated from GVHD animals responded to immobilized anti-CD3 and 56% (220 of 396) of these hybridomas responded specifically to APC expressing host bm1 or bm12 alloantigens. More than 80% of bm12-specific hybridomas expressed CD4; all (53 of 53) of the bm12-specific hybridomas tested reacted to homozygous bm12 APC. Of the alloreactive T hybridomas generated from B6-->(bm1 x bm12)F1 GVHD mice, 7% responded to bm1 APC. Five bm1-specific hybridomas were analyzed further. One CD4+ hybridoma recognized a bm1 peptide presented by self I-Ab and was blocked by anti-Ia Ab; the other four hybridomas, two of which also expressed CD4, responded to transfected L cells expressing H-2Kbm1 and were not inhibited by anti-Ia Ab. These results indicate that a high percentage of CD4+ T hybridomas generated from freshly isolated T cells activated in vivo during GVHD are specific for host MHC class II or class I alloantigens.